The present invention relates to control valves, and more particularly to control valves and actuator devices for operation of the control valves. Even more particularly, the present invention relates to control valves and actuators for use in ultra pure applications.
The need for high purity chemical handling equipment is well established in the semiconductor industry. The degree to which a control valve, also referred to as a valve, is a high purity valve is measured by the contamination that it contributes to a gas or liquid stream that passes through the control valve. The difference in chemical content between what enters the valve and what leaves the valve is contamination, which may be either in a gas phase or fluid phase. There are essentially three sources of contamination associated with such valves.
First, the valve may leak atmospheric gas (e.g., air) into the liquid or gas stream (i.e., the material flow or the process flow), which is commonly referred to as an outboard leak. This is disadvantageous in that air, which contains about 1.5% moisture can contaminate the process flow. Typically, such outboard leaks occur due to actuation devices that allow the external environment access to the interior of the valve.
A second source of contamination is the valve may leak across a valve seat, which is commonly referred to as an inboard leak. This may lead to back streaming of other gases or fluids into a process gas or fluid or may lead to leakage of gas or fluid when it is not desired into a process, resulting in the presence of an otherwise desired chemical at the wrong time. Valves commonly leak across the valve seat due to a mis-alignment of a valve head-member and the valve seat or due to wear of the valve seat and the valve head-member or decomposition of particle matter on the valve seat.
A third source of contamination is the valve material itself may degrade and enter the gas or fluid stream. Valve components that are made of metal may degrade and contribute metallic contamination. Valve components made of elastomeric materials may degrade and contribute this as contamination. Such types of degradation may be further enhanced by the corrosive nature of the gas or liquid stream passing through the valve. Thus a high purity control valve is needed that minimizes these sources of contamination.
The present invention advantageously addresses the above and other needs.
The present invention advantageously addresses the needs above as well as other needs by providing a self-aligning, compact valve assembly for use in ultra pure applications which minimizes various sources of contamination over a wide temperature range.
In one embodiment, the invention can be characterized as a shut-off valve assembly including a hollow valve body having a first opening and a second opening, a valve seat positioned within the hollow valve body proximate to the first opening, and a first diaphragm assembly. A deflectable portion of the first diaphragm assembly is attached to an interior surface of the hollow valve body forming a first volume between the valve seat and the first diaphragm assembly. A second diaphragm is attached to another portion of the interior of the hollow valve body and attached to the first diaphragm assembly such that a second volume is defined between the second diaphragm and the second opening. A third volume is formed between the first diaphragm assembly and the second diaphragm and is sealed from the first volume and the second volume by the first diaphragm assembly and the second diaphragm. At least one flow hole is formed in the first diaphragm assembly and allows a process flow to flow between the first volume and the second volume. A self-aligning head assembly is also included which comprises a stem attached at a first end to another portion of the first diaphragm assembly and a valve head coupled to a second end of the stem. The valve head is adapted to self-align into the valve seat with a leak rate of less than or equal to 4xc3x9710xe2x88x929 atmosphere cc of Helium/sec. And a deflection of the deflectable portion of the first diaphragm assembly and the second diaphragm allows the other portion of first diaphragm assembly to move in order to open and close the valve head from the valve seat.
In another embodiment, the invention may be characterized as a valve assembly comprising a hollow valve body having a first opening and a second opening, a valve seat positioned within the hollow valve body, and a first diaphragm assembly having a ring portion and a sleeve portion. A perimeter of the ring portion is attached to an interior surface of the hollow valve body such that a first volume is defined between the valve seat and the first diaphragm assembly. A second diaphragm is attached at a perimeter surface to the another portion of the interior of the hollow valve body and attached to the sleeve portion such that a second volume is defined between the second diaphragm and the second opening. A third volume is formed between the first diaphragm assembly and the second diaphragm and is sealed from the first volume and the second volume by the first diaphragm assembly and the second diaphragm. At least one flow hole is formed in the sleeve portion and allows a process flow to flow between the first volume and the second volume. A self-aligning head assembly is also included and comprises a stem coupled at one end to the first diaphragm assembly and a valve head coupled to another end of the stem. The valve head is adapted to self-align into the valve seat. And an actuator assembly is coupled to the first diaphragm assembly and the second diaphragm for deflecting the ring portion of the first diaphragm assembly and the second diaphragm which moves the sleeve portion and which controls the position of the valve head relative to the valve seat.
In a further embodiment, the invention may be characterized as a valve assembly comprising a hollow valve body having a first opening at one end of the hollow valve body and a second opening at an opposite end of the hollow valve body. A valve seat is positioned within the hollow valve body. Also included is a first diaphragm assembly having a ring portion and a sleeve portion. The perimeter of the ring portion is attached to an interior surface of the hollow valve body such that a first volume is defined between the valve seat and the first diaphragm assembly. A second diaphragm is attached to the another portion of the interior of the hollow valve body and attached to the sleeve portion of the first diaphragm assembly such that a second volume is defined between the second diaphragm and the second opening. A third volume is formed between the first diaphragm assembly and the second diaphragm and is sealed from the first volume and the second volume by the first diaphragm assembly and the second diaphragm. At least one flow hole is formed in the sleeve portion, and allows a process flow to flow between the first volume and the second volume. A valve head is coupled to the sleeve portion and is adapted to seal into the valve seat. An actuator assembly is coupled to the first diaphragm assembly and the second diaphragm for deflecting the ring portion of the first diaphragm assembly and the second diaphragm which moves the sleeve portion and which controls the position of the valve head relative to the valve seat. A surface area of the ring portion facing the first volume is approximately equal to a surface area of the second diaphragm facing the second volume, such that a first force exerted on the ring portion by the process flow in the first volume substantially cancels a second force in the opposite direction exerted on the second diaphragm by the process flow in the second volume. Thus, the first diaphragm assembly and the second diaphragm are substantially balanced with respect to the pressure of the process flow.
In yet another embodiment, the invention may be characterized as a valve assembly comprising a hollow valve body having a first opening at one end of the hollow valve body and a second opening at an opposite end of the hollow valve body, and a valve seat positioned within the hollow valve body proximate to the first opening. Also included is a first diaphragm assembly having a ring portion and a sleeve portion extending away from the ring portion. A perimeter of the ring portion is attached to an interior surface of the hollow valve body such that a first volume is defined between the valve seat, the sleeve portion and the first diaphragm assembly. A second diaphragm is attached at a perimeter surface to the another portion of the interior of the hollow valve body. The second diaphragm includes a hole, wherein an end portion of the sleeve portion extends through the hole and the second diaphragm is attached to the sleeve portion at the hole. A second volume is defined between the second diaphragm, the end portion of the sleeve portion and the second opening. A non-gas wetted volume is formed between the first diaphragm assembly and the second diaphragm and is sealed from the first volume and the second volume by the first diaphragm assembly and the second diaphragm. At least one flow hole is formed in the end portion of the sleeve portion and allows a process flow to flow between the first volume and the second volume. Also included is a self-aligning head assembly comprising a flexible stem coupled at one end to the sleeve portion and a valve head coupled to another end of the flexible stem. At least a portion of the valve head is spherical and is adapted to self-align and seal into the valve seat with a leak rate of less than or equal to 4xc3x9710xe2x88x929 atmosphere cc of Helium/sec at temperatures up to 1000 degrees centigrade. An actuator assembly is coupled to the first diaphragm assembly and the second diaphragm for deflecting the ring portion of the first diaphragm assembly and the second diaphragm which moves the sleeve portion in order to open and close the valve head from the valve seat. The actuator assembly provides an actuating force axial to the movement of the process flow through the hollow valve body. Also, the process flow generally flows in-line through the hollow valve body between the first opening and the second opening via the first volume and the second volume. A surface area of the ring portion facing the first volume is approximately equal to a surface area of the second diaphragm facing the second volume, such that a first force exerted on the ring portion by the process flow in the first volume substantially cancels a second force in the opposite direction exerted on the second diaphragm by the process flow in the second volume. Thus, the first diaphragm assembly and the second diaphragm are substantially balanced with respect to the pressure of the process flow.